function y = specA1d(u,V)
N = length(V);
h = 1 / N;
kvec = fftshift(((-N/2):(N/2-1))');
ud2 = 4*pi.^2*repmat(kvec.^2,1,size(u,2)).*fft(u,[],1)*h;
ud2 = ifft(ud2,[],1)*N;
y = real(repmat(V,1,size(u,2)).*u + ud2);
